So, You have NGINX configured to gzip all your requests.
Be careful that your Drupal services could be sending the wrong content-length, Drupal's xmlrpcs.inc is sending the content-length of the request BEFORE nginx gzip's the output.
This means your XMLRPC clients will be left hanging, waiting for the rest of the transmission but never getting it.
POST /services/nodeSubmit HTTP/1.1
User-Agent: xmlrpclib.py/1.0.1 (by www.pythonware.com)